Interactions of sulfur oxidation repressor with its promoters involve different binding geometries

Arch Microbiol. 2012 Sep;194(9):737-47. doi: 10.1007/s00203-012-0808-z. Epub 2012 Apr 6.

Abstract

The divergently transcribed sulfur oxidation (sox) operon of a sulfur chemolithotrophs, Pseudaminobacter salicylatoxidans KCT001, comprising sox TRS-VW-XYZABCD, is regulated by a repressor (SoxR). SoxR binds to two disparate operators, sv (present in between soxS and soxV) and wx (present in between soxW and soxX). Here we report details of the interaction between SoxR and these two operator regions of the sox operon, using methylation interference and hydroxyl radical footprinting. We propose that the sv operator is symmetric and compact, while the wx operator is asymmetric and extended. We report an interesting difference between the SoxR-sv interaction and the SoxR-wx interaction through a competition assay involving groove-specific ligands. SoxR binds in the major groove of the sv operator, but binds in the minor groove of the wx operator. The structural flexibility of the SoxR helps it to act differentially in its interactions with these two operators. Mutational analysis shows that SoxR uses different amino acid residues when binding to the sv operator versus the wx operator. Taken together, the results indicate that interaction between SoxR and the two operator sites involves different binding geometries. This makes SoxR the only known example of a ArsR-family protein that binds differentially to different operators.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Bacterial Proteins / genetics
  • Bacterial Proteins / metabolism*
  • Base Sequence
  • DNA Mutational Analysis
  • Operon / genetics*
  • Oxidation-Reduction
  • Phyllobacteriaceae / genetics
  • Phyllobacteriaceae / metabolism*
  • Promoter Regions, Genetic / genetics*
  • Protein Binding
  • Repressor Proteins / genetics
  • Repressor Proteins / metabolism
  • Transcription Factors / metabolism*

Substances

  • Bacterial Proteins
  • Repressor Proteins
  • Transcription Factors
  • SoxR protein, Bacteria